Update: GIGAOM on rPath Burns EC2 Appliances in a Web Portal. rBuilder adds a portal that lets users turn software into virtual appliances.
rPath demoed their virtual appliance management system at Monday's AWS Meetup. What they do is help you build a generic virtual machine image deployable on Amazon, VMWare, Xen and other targets. The idea is to build your software application independent of the underlying operating system and deploy it in your own or someone else's datacenter without worrying about all the details.
To put their service in context think of rPath as how you build, deploy, and upgrade images and someone like Right Scale has how you can run and managed a cluster of deployed images.
To build a Virtual Appliance you pull together all your packages through their web interface or through a Python based "recipe" system, select a VM target, and "cook" it all into a VM image you can immediately deploy and run.
To make this magic happen they use the Conary package manager system and they have their own RedHat compatible OS. One of their major features is a very fine grained package management systems which allows them to perform minimal inplace upgrades of deployed images. The downside is you must use their packaging system and their OS for this to work. Any code you want to install must be installable using their packaging system.
There's a free community version available on their website for Open Sourcers.. They make their money from people buying a Virtual Appliance of their build and packaging system and deploying it internally. So you can integrate their Virtual Appliance system as part of your build and deployment infrastructure. As part of your nightly build create appliances and have them automatically deployed to your test jigs. Once testing is complete you can deploy into your datacenter.
Their smart upgrade features are very nice for a datacenter. Usually package management during upgrades is a complete nightmare. For cloud deployment I think this feature is less useful as I would simply create a new image, fire up a new instance using the new image, and bring down my old images without the cost of a software upgrade. Of course you still have to worry about protocol and data compatibilities.
rPath's Virtual Appliance is kind of a hard idea to really understand because it still ahead of curve of what most people are doing. But I think as we move into a world of multiple clouds we must seed with our images, a layer above the clouds is necessary to manage the whole process. rPath is saying we've already built that layer so you don't have to.